The present invention relates to a saw which has a saw blade provided on its outer edge with a single or multi-part hard metal or diamond-containing cutting coating.
Saws of this general type are widely known and used for separation of metal, stone or wood. There are circular saws with uninterrupted enclosed cutting coating or with a cutting coating which is subdivided into a plurality of segments. There are also cross-bar saws which are used for working of stone. There are also saws with inner holes for separating thin discs. These saws include normally a saw blade composed of steel.
The manufacture of saws with a saw blade of steel is connected for various reasons with considerable expenses. For forming a saw blade, the steel sheet must be first edged and milled. Then it must be ground and subjected to a thermal treatment as well as clamped and oriented. In addition, it can be adjusted to have a high tension, so that during use the saw does not deform since bending of the saw blade lead to variation of a cutting path.
When the saw blade has a sufficient thickness, there is a disadvantage that the steel possesses a relatively high specific weight of 7.5-8. This leads especially for large and fast rotatable saws to occurrence of high inertia forces which contributes to the deformation of the saw blades.
A further disadvantage of the known saw blades of steel resides in their high noise level which lead to resonance vibrations produced by the homogeneity of the steel material. Important are moreover the high considerable transportation costs connected with the high weight of saws especially when they have great diameters.
Finally, it has to be taken into consideration that the saws with a saw blade of steel and a cutting coating of diamond or cubic crystalline boron nitride which is generally comparable with diamonds has the high danger of rusting the reason is that they operate in a wet environment for cooling of the diamond coating, supply cooling water which is distributed on the saw blade. The rust can affect the firm hold of the high grade diamond cutting segments on the saw blade. This is especially true when the high grade diamond cutting bodies are connected with the saw blade by special carriers which are advantageous for some reasons. Taking the above into consideration attempts have been made to produce saws with the use of synthetic plastic materials.
The German document DE-OS 27 40 891 shows a saw which has a hub of a ring-shaped metal core and a metallic outer ring supporting the cutting bodies. On the hub and the outer ring, radially extending filaments or wires are mounted which connect these parts with one another. Connecting members are embedded in synthetic plastic material after manufacture of the construction. It is to be understood that the arrangement, orientation and clamping of the wires involves considerable expenses. The reason is that the centering of the outer metal ring relative to the inner ring must be ensured before the synthetic plastic is cast or pressed into the intermediate space.
Considerable expenses are required for the production of a known cutting off disc of synthetic plastic in which the grinding grains are directly embedded in a synthetic plastic material reinforced with carbon fibers. This saw is disclosed in the German document DE-OS 28 29 609. In this arrangement the saw blade does not form a carrier for the cutting segments or a cutting coating as in conventional saws. Such grinding discs are also not suitable for the use for grinding grains of diamonds which require a metallic binding, for example saws with greater diameters used for separation of steel or metal. In the known saws the cutting blades arranged on the periphery of the saw are replaced after their use with others as in the case of utilization of diamond grains held in cutting segments which are supported on the saw blade. Saws with high output due to their high diamond concentration cannot be produced in accordance with the known design from synthetic plastic material, since because of a sufficient binding the grinding grains do not make possible a high fiber fraction for reinforcing of the synthetic plastic. In addition, in such cutting off discs, together with the grinding grain also the grinding sheet or saw blade is consumed, in contrast to saws carrying continuous cutting coating or segments on their periphery which can be replaced after the use.